Laura Nocka

All Publications

• Stimulation of the catalytic activity of the tyrosine kinase Btk by the adaptor protein Grb2 ELIFE Nocka, L. M., Eisen, T. J., Iavarone, A. T., Groves, J. T., Kuriyan, J., Murphy, J. M. 2023; 12

  Abstract

  The Tec-family kinase Btk contains a lipid-binding Pleckstrin homology and Tec homology (PH-TH) module connected by a proline-rich linker to a 'Src module', an SH3-SH2-kinase unit also found in Src-family kinases and Abl. We showed previously that Btk is activated by PH-TH dimerization, which is triggered on membranes by the phosphatidyl inositol phosphate PIP3, or in solution by inositol hexakisphosphate (IP6) (Wang et al., 2015, https://doi.org/10.7554/eLife.06074). We now report that the ubiquitous adaptor protein growth-factor-receptor-bound protein 2 (Grb2) binds to and substantially increases the activity of PIP3-bound Btk on membranes. Using reconstitution on supported-lipid bilayers, we find that Grb2 can be recruited to membrane-bound Btk through interaction with the proline-rich linker in Btk. This interaction requires intact Grb2, containing both SH3 domains and the SH2 domain, but does not require that the SH2 domain be able to bind phosphorylated tyrosine residues - thus Grb2 bound to Btk is free to interact with scaffold proteins via the SH2 domain. We show that the Grb2-Btk interaction recruits Btk to scaffold-mediated signaling clusters in reconstituted membranes. Our findings indicate that PIP3-mediated dimerization of Btk does not fully activate Btk, and that Btk adopts an autoinhibited state at the membrane that is released by Grb2.

  View details for DOI 10.7554/eLife.82676

  View details for Web of Science ID 000979979300001

  View details for PubMedID 37159508

  View details for PubMedCentralID PMC10132808

• Coupled Membrane Lipid Miscibility and Phosphotyrosine-Driven Protein Condensation Phase Transitions. Biophysical journal Chung, J. K., Huang, W. Y., Carbone, C. B., Nocka, L. M., Parikh, A. N., Vale, R. D., Groves, J. T. 2020

  Abstract

  Lipid miscibility phase separation has long been considered to be a central element of cell membrane organization. More recently, protein condensation phase transitions, into three-dimensional droplets or in two-dimensional lattices on membrane surfaces, have emerged as another important organizational principle within cells. Here, we reconstitute the linker for activation of Tcells (LAT):growth-factor-receptor-bound protein 2 (Grb2):son of sevenless (SOS) protein condensation on the surface of giant unilamellar vesicles capable of undergoing lipid phase separations. Our results indicate that the assembly of the protein condensate on the membrane surface can drive lipid phase separation. This phase transition occurs isothermally and is governed by tyrosine phosphorylation on LAT. Furthermore, we observe that the induced lipid phase separation drives localization of the SOS substrate, K-Ras, into the LAT:Grb2:SOS protein condensate.

  View details for DOI 10.1016/j.bpj.2020.09.017

  View details for PubMedID 33080222